I was using 1.5 with Ian's updated files. Still didn't work. I originally tried 2.5 (before I knew about Ian's files) and switched to 1.5 because doing so allowed me to complete one of the earlier missions. That was before I knew anything about ME, but I spent so much time googling how to complete the missions I learned about this site, those updated files, and how to use ME at least for some basics. After I learned about that, I stayed on 1.5, downloaded the files, and kept going through the missions.
Maybe it's better if you start in 2.5 with the files, but at the time I wasn't aware of any of that, and eventually I made it to 1.5 with files installed, still wayyy too much time spent editing instead of flying.
But as I said, my hope was just to prevent someone from having the same headaches I did and bypass the campaign altogether, and do Georgian War instead.